In cold rolling metal strips under tension, especially when using small diameter work rolls, the edges of the strip have a tendency to become over-rolled, due to work roll deflection. When the strip edges are elongated to a greater extent than the strip center, the strip edges will tend to buckle.
The most usual prior art remedy for this problem has been to provide upper and lower backing rolls having tapered reliefs at opposite ends so as to accommodate both edges of the strip. Generally, means are also provided for shifting the backing rolls axially so as to position their reliefs appropriately with respect to the strip edges, depending upon the width of the strip being rolled.
The present invention is based upon the discovery that the upper and lower work rolls, themselves, can be provided with adjustable reliefs. The adjustable reliefs of the upper and lower work rolls being at opposite ends thereof to accommodate both edges of the strip being rolled. The reliefs are readily adjustable through the agency of hydraulic means, so that the same work rolls can accommodate strips of various widths.
The adjustable relief work rolls of the present invention have a number of advantages. First of all, no axial shifting of rolls is required. The invention can be applied to relatively large diameter work rolls, such as are used on four-high mills. The mill, itself, is simplified because the reliefs are provided within the work rolls, themselves, and no extra rolls are required. Finally, the invention can be applied to existing four-high and six-high strip mills, by leaving the backing rolls in tact and installing the work rolls of the present invention.